Water Deprivation

• The Leyland cypress tree can be planted in full to partial sunlight and is usually drought tolerant. This does not mean, however, that it does not need to be watered. Young or newly planted trees, especially under 1 year old, may still be establishing their root system. During this time, make sure the tree gets adequate watering. If you live in a region where drought or infrequent rain is the norm, water your Leyland cypress once a week, especially during the summer months. If you feel the soil and it is completely dry to the touch, water your tree.
  
  

Stress

• Though the Leyland cypress tree is not prone to many diseases, those diseases that do affect the tree usually occur during times of stress. To avoid stress for the tree, and therefore avoid diseases, make sure the tree is properly mulched and watered year round, especially during times of drought. In addition, it's a good idea to avoid heavy fertilization of the Leyland cypress. The chemicals could create stress in the tree, and attract cankers.
  
  

Cercospora Needle Blight

• Cercospora needle blight is caused by a fungus, usually during extended times of wet and rainy weather. The main symptom of this disease is a browning of the needles very near to the stem. The worse or more progressed the fungus is on the Leyland cypress, the further the brown needles extend outward. The fungus can also cause green pustules to appear on the upper portions of the needles, which is an important sign in distinguishing this disease from others that may affect the Leyland cypress. The disease can be controlled with a fungicide that contains copper. If used in ten-day cycles, the fungicide may stop the fungus from spreading while new needle growth takes over.
  
  

Botryosphaeria Canker

• The Botryosphaeria Canker almost always infects small twigs and branches on the Leyland cypress, turning them dull red and brown. You can tell a canker apart from a needle blight or other fungi because the needles are usually not affected, and the browning will occur on the branches and trunk. The Botryosphaeria canker almost always occurs on trees that are undergoing severe stress, and the only cure is to try to keep the tree healthy, avoiding the canker altogether. This includes adequate watering and low to no fertilization.
  
  

Seirdium Canker

• Seirdium canker is the most damaging of the few diseases affecting the Leyland cypress. The disease penetrates needles, stems and branches, and can turn large patches of the tree dark brown. The most common way that the Seiridium canker is spread is through pruning tools, though if the tree is severely lacking water, the fungus may easily infect the tree. To rid the tree of the cankers, you can cut them away with pruning tools, though the pruning tools must be sanitized after each cut in a bleach and water solution. If the tree is severely browned, the infection will not be able to be cured, and the tree should be removed to prevent the fungus from spreading to other trees.